1. Field of the Invention
The present invention relates to heat-laminating composite films comprising a layer of a saponified product of ethylene-vinyl acetate copolymer having a specific composition and two specific adhesives and comprising a specific construction, which are excellent in anti-blocking properties and adhesion properties, have solved a problem of slippage and can be advantageously provided for practical use, and also to laminated materials using the same.
2. Description of the Prior Art
It is generally known that films or sheets of plasticized polyvinyl chloride, ordinarily called non-rigid polyvinyl chloride, hitherto employed, in industry contain plasticizer in large quantities more than about 25 wt%, in most cases, more than 30 wt%. For this reason, the sheets and the like encounter a serious drawback that the plasticizers bleed out of the surface when they have been extensively used. Therefore coating materials which coat the surface to eliminate the drawback have been deemed desirable.
When that non-rigid polyvinyl chloride sheet is used for, e.g. desk mat or paper holders, printing ink adheres to the non-rigid polyvinyl chloride sheets in an extremely short period of time when the sheet is brought into contact with reproduced documents by an electrostatic copying machine so that problems arise in that documents are obscured or the non-rigid polyvinyl chloride sheet is contaminated thus making reading-out of characters or the like on the printed surface impossible. Also in furniture, office fixtures, etc. prepared from or coated with so called vinyl chloride leather materials composed of non-rigid polyvinyl chloride or in wallpaper substantially composed of non-rigid polyvinyl chloride, etc., staining tends to occur due to bleeding the plasticizer out of the surface, which results in additional problems because such staining can be wiped out only with difficulty. Furthermore, films or sheets of non-rigid polyvinyl chloride have been advantageously employed as agricultural film or sheet for houses for crop cultivation, gardening facilities such as tunnels, multiples, etc., because of their excellent heat insulation property as compared to films or sheets of polyolefin or the like. However, the use of the films or sheets over a long term period results in drawbacks that plasticizers bleed out of the surface to stain so that transmission of light decreases, resulting in similar technical problems. Many attempts to improve the problem have been made but products which achieve the object and can be satisfactorily provided for practical use have not been found yet and, therefore films or sheets of non-rigid polyvinyl chloride free from bleeding of plasticizers out of the surface would be desirable.
On the other hand, an attempt to eliminate the drawback by laminating other thermoplastic film on a film or sheet comprising the non-rigid polyvinyl chloride has been also made. As laminating film for practical application, there is acrylic resin film capable of easily adhering to film or sheet consisting essentially of non-rigid polyvinyl chloride by the heat lamination process. However, no substantial effect of preventing bleeding of plasticizers has been attained. Other thermoplastic resins cannot be adhered to and coated onto films or sheets of non-rigid polyvinyl chloride through the heat lamination process which is easy, readily acceptable for manufacturers for films or sheets of the polyvinyl chloride type, technically most simple and easily adoptable, unless adhesives are used. From the foregoing situations, there is a strong desire for a heat-laminating composite film to which coating can be effected with a good adhesive force directly by the heat lamination process as with the foregoing acrylic resin, without requiring the manufacturers to use coating adhesives, and to give a composition in which bleeding of plasticizers can be prevented.
Further it is disclosed in Published Examined Japanese Patent Application No. 38103/78 that a biaxially stretched polyvinyl alcohol film having excellent water resistance property and free from occurrence of curling, wrinkling, etc. can be obtained by coating a solution of a blend of an isocyanate group-containing reactive polyurethane and a vinyl chloride-vinyl acetate copolymer in an organic solvent on a film of biaxially stretched polyvinyl alcohol type to form a coated layer and coating on the resulting coated layer an aqueous dispersion of a vinylidene chloride copolymer of a vinyl chloride-vinyl acetate copolymer. However, there is no disclosure that a heat-laminating composite film would be obtained by coating a solution of a blend of an isocyanate group-containing reactive polyurethane and a vinyl chloride-vinyl acetate copolymer in an organic solvent onto a saponified product of ethylene-vinyl acetate copolymer to form a heat-laminating composite film, or further that the composite film would be laminated onto a plasticized polyvinyl chloride film or sheet and that bleeding of a plasticizer in polyvinyl chloride can be prevented by such lamination.